Although not exclusively, this invention particularly concerns aircraft piloting systems and shall hereafter be described in greater detail with reference to such an application, it being understood that this application does not in any way limit the scope of the invention.
A large number of machines, such as planes, helicopters, tanks, civil engineering engines, etc., are provided with a set of controlled elements able to be activated from either of the two connected operators stations controlled by two separate operators (known as the pilot and copilot in the cases of vehicles) and each equipped with a stick type control member articulated so as to be able to pivot in any direction. These two control elements are connected to said members to be controlled and are interconnected so that each of said operators has available the set of the controls of said members to be controlled and so that the deliberate tilting by an operator directly activating one of said control elements results in an identical induced tilting in the same direction of the other control member.
Up until now, the transmission of control orders between a stick activated by an operator and an element to be controlled has been effected mechanically, which required that said sticks needed to be relatively large and were able to bear and transmit large mechanical forces. Such sticks were thus provided directly in front of said operators, were held by both hands of each operator and were activated via a forearm movement of the latter, the amplitude and intensity of their movements being conditioned by the resistances to be mastered so as to handle mechanical controls.
The use of both hands of each operator made it possible, not only to transmit significant forces, but also rendered these forces symmetrical and identical for the two operators.
However, mechanical controls have increasingly been replaced by electric controls having a large number of advantages, relating to certain elements, such as weight, spatial requirement, maintenance, the taking into account of complex control laws, etc. As a result, said sticks are connected to and associated with electric sensors which detect the position variations of said sticks and which control electric controls activating said controlled members according to information supplied by said sensors. In these circumstances, said sticks only transmit extremely small forces and their dimensions and mechanical resistance are able to be considerably reduced. This is the reason why small sticks are now useD, said sticks being known as "minicolumns" or "ministicks" and being able to held and activated by a single hand of an operator. Since these ministicks only transmit small forces and so as to enable said operators to determine the forces they apply to a ministick in order to cause it to tilt and bring it back to a netural position once it is released, it has been necessary to provide at least one force sensation device constituted, for example, by a spring rod.
In addition to the advantages mentioned above concerning the use of electric controls, such ministicks make it possible to free the space in front of the operators so as to optimize the grouping of the other controls in front of said operators, each ministick being disposed laterally in relation to said operators, Furthermore, especially when the two control stations of the operators are parallel (this usually being the case in a vehicle in which said stations are disposed opposite the front of the latter) so as to observe the symmetry of the machine with respect to an axis passing between said stations, one of the ministicks is disposed at the left of the leftside operator and the right ministick is disposed at the right of the rightside operator. In such a case, the leftside operator thus holds the associated ministick in his left hand, whereas the righTside operator holds his ministick in his right hand. Observance of the symmetry of the control of the machine thus results in aN asymmetry at the plane of the operators.
Such as asymmetry causes difficulties when the control of the machine requires lateral tiltings of the ministicks from left to right and vice versa with respect to said operators. This most certainly arises from the human morphology which means that the possibilities for exerting a lateral force by a given hand closed on a ministick differ, depending on whether the force is exerted by pushing inwardly with the palm or by pulling outwardly with the fingers. Moreover, in the disposition described above, a pushing with the palm in one of the control stations corresponds to a traction with the fingers in the other station.
Accordingly, not merely the lateral pushing and traction shall be experienced differently by each operator, but also the asymmetry of the forces is inversed when an order with the left hand at the lefthand station is recorded by a control with the right hand at the righthand station and vice verse. The passing of the order of the machine from one control station to the other is thus effected accompanied by jerks, which may result in serious consequences, especially where an airplane is involved.
So as to overcome these drawbacks, it has already been proposed to provide in a complex machine with a mechanical conjugation and two ministicks a force sensation device connected to each of said control elements so that the force sensation device connected to the control member activated by the left hand is only active when the latter is deliberately and directly activated by an operator from left to right and when the force sensation device connected to the control member activated by the right hand is active when the latter is deliberately and directly activated by an operator from right to left.
Such a twin-ministick mechanical conjugation device provided with complex selective action force sensation devices proves to be satisfactory. However, owing to its mechanical structure, it does not make it possible to optimize the embodiment in an electric form of flight controls. Moreover, this devicE exhibits quite considerable plays and frictions with respect to the clearances and forces employed, and the inertia of moving parts adversely affects correct functioning so that its performances, especially as regards piloting precision, are not as good as one could hope for.
Furthermore, in the event of a deliberate tilting of a stick by an operator, so as to ensure that an induced identical tilting in the same direction is applied to the other stick (position recopying), it is necessary to either provide special motors or to add to this effect the mechanical conjugation device between the two sticks. In any event, such motors are required when the vehicle (airplane) comprises an automatic pilot so that the position of the ministicks corresponds at all times to the control of the automatic pilot.
In addition, it is often necessary to connect to each of said sticks for each of their tilting axes aT least one damper so as to perfect the tiltings of the latter, to limit too rapid displacements and to avoid oscillations which might adversely affect control.
Finally, so as to warn airplane pilots of an anomaly or a flight danger, it is common usage to connect vibrators to said sticks driving the vibration of said sticks. As a result, the operator holding a stick in his hand is aware of these vibrations and is able to take any necessary corrective steps.
Thus, one can easily see that the ministick control devices are complex devices comprising, as they do, force sensation devices (spring rods, leaf springs, scissors, etc), dampers (hydraulic, membrane, friction, etc), motorization means for recopying the automatic piloting phase position or for recopying from one piloting station to another, and vibrators.